What's being said is this:
Your TIR head is in the center of a sphere. You can swivel your head left or right and remain in the center of the sphere. In some planes, the default centered head position is either too close or too far from the instrument panel for some people. If you move your head closer, then re-center TIR, the center of the sphere is closer to the front of your cockpit. When you move back to your normal (not leaning forward anymore) position, you are no longer in the center of the TIR sphere. When you swivel your head left or right, because you are no longer in the center of the sphere, the view doesn't rotate as it should.